Researcher probes complex interactions of disease and organ
Host Amber Smith: Upstate Medical University in Syracuse New York invites you to be "The Informed Patient" with the podcast that features experts from Central New York's only academic medical center. I'm your host, Amber Smith. The National Institutes of Health awarded a grant to an MD/PhD student at Upstate who is researching lupus. Here with me to explain his work is Akshay Patel, who works in the lab of Dr. Andras Perl. Welcome to "The Informed Patient," Mr. Patel.
Akshay Patel: Thanks for having me.
Host Amber Smith: People may have heard of lupus without knowing exactly what it is. Can you give us a bit of a summary?
Akshay Patel: Sure. So, lupus is an autoimmune disease. It's a shortened form of a much bigger kind of word: systemic lupus erythematosus. That's kind of what I study. Lupus is a more broader term.
It's an autoimmune disease. So think of, say you get a cut, like a paper cut or something, And maybe some bacteria or some debris find its way into that cut. This could be devastating for your body. Those bacteria or those pathogens that get in there could cause an infection. Your body has a system and it's kind of built in, in order to protect you from that happening. And it's the immune system. The immune system comes in, and it is able to clear out the bacteria or the debris or the pathogens. And sometimes the immune system is defective. Sometimes it doesn't work. And sometimes it actually is directed toward the wrong stuff. And in an autoimmune disease, your immune system, which is supposed to protect you from foreign invaders, so to speak, actually ends up attacking you. It attacks yourself.
And that's kind of the basis of what underlies lupus, where the immune system attacks the body. It attacks a variety of different organ systems like the kidney, the heart, the lungs, and of course the liver, which is what I study.
Host Amber Smith: I was going to ask you about what the hallmark symptoms are. It sounds like they're all, all over the place.
Akshay Patel: They are. Typically, mostly it affects the skin. I'd say 80 to 90% of patients with lupus have some sort of skin involvement. But it can also affect the heart, the lungs. It can affect the brain and the kidney. The larger term, as I said, is systemic lupus erythematous, and truly it is systemic, as it affects a variety of different organ systems and organ compartments.
Host Amber Smith: Well, how common is lupus and who does it affect?
Akshay Patel: Overall, autoimmunity affects about 3 to 5% of the population. So that's, a pretty significant number. And when we think of lupus, or systemic lupus erythematosus, that affects anywhere from 20 to 150 of 100,000 individuals pretty much worldwide. So there's a wide range. It's rare, but it's definitely an important subset of people.
And who does it affect? That's a very interesting question. Autoimmune diseases, typically, they preferentially are seen in women, and particularly they're diagnosed in women of childbearing age because there's a huge component of estrogen and estrogen signaling that can predispose to a lupus or can exacerbate these kind of autoimmune diseases in susceptible individuals. Last I checked, it was a 9-to-1 ratio of women to men.
Host Amber Smith: Interesting. Do we know yet what causes lupus?
Akshay Patel: There are a lot of different factors that come into play. Say you have a staph infection, well, it's staph, so you just affect staph, and you don't have the infection anymore. But it's considerably more complicated with lupus. As I mentioned, it's multi-systemic, multiple different organ systems. And so there are a variety of different factors that come into play to kind of cause lupus. We can think of genetic factors, environmental factors, even hormonal factors. As I said earlier, estrogen is extremely important in the pathogenesis of lupus. Even things like epigenetics where not only is it the DNA code, but how the DNA itself is modified. All of these things can come together to kind of cause a dysfunction in the immune system.
We'll see an increase in antibodies, which are these proteins that the immune system generates to fight off an infection or to cause, promote an immune response. We'll see a dysfunction in T-cells, which is really where my focus is. T-cells are a particular subset of immune cells, which when they're dysfunctional, can cause an autoimmune attack. As well as we can see the deposition of these things called immune complexes, where those antibodies that I talked about earlier can congregate together, and then that can also cause or facilitate an immune response or immune attack. All of these things come together to then, like I said, kind attack different organ systems.
Host Amber Smith: This is Upstate's "The Informed Patient" podcast. I'm your host, Amber Smith. I'm talking with Akshay Patel. He's an MD/PhD student working in the lab of Dr. Andras Perl at Upstate, and we're talking about his research into lupus.
So how did you decide to focus on the impact lupus has on the liver?
I kind of fell into it. Funny story, I guess. I kind of have a mouse phobia. I'm afraid of mice. So, graduate students in the lab typically would go down to the mouse colony and get samples. Typically, it's urine. So as I said earlier, lupus affects the kidney. That's a major organ that's affected in lupus, and we're able to actually track renal involvement of lupus by measuring the amount of protein that's in their urine.
Akshay Patel: But I'm afraid of mice and have a phobia. So I used to find ways to not go down to the mouse colony, and I think Dr. Perl picked up on that. So he said, "Look, you don't have to go down there. There are these histology slides of mouse livers. Take a look at them to see if there's anything interesting." I took a look at them, and I saw that lupus livers had inflammation in them more so than the non lupus livers.
The enzyme that I work on, this rab4a enzyme, was linked to the amount of inflammation that was in their livers. And so I quantified it, and then we repeated the experiments, and it was pretty consistent. And that's kind of how I fell into it.
What's also interesting is that, We talked about all of these other manifestations. The skin manifestations, 80 to 90% of lupus patients have some sort of skin manifestation. Renal manifestation, 50 plus percent of lupus patients have some sort of renal involvement. When I started my PhD, we knew that only about 20% of lupus patients had some sort of liver involvement. And I say "only." You know, I don't want to discount the patient's experience, but we have to keep in mind that if we compare it to other manifestations, the liver is very understudied. Now we've learned that the involvement of the liver could be upwards of 30 to 40% of lupus patients. But back then it was understudied. And it was very interesting that this enzyme that we studied was kind of controlling the amount of inflammation that was in lupus livers.
Host Amber Smith: Can you, before we get into this a little bit more, can you review for us what role the liver has in our body? What is it responsible for?
Akshay Patel: Sure. So imagine, you're eating. And imagine your gut is like a tube. So you eat, and your food goes down into your mouth, from your mouth into the esophagus, and the stomach, duodenum, jejunum, ileum, goes into the large intestine. And as this is happening, your intestines are kind of absorbing the nutrients that are in your food. But it doesn't go directly into the blood. There's like a net that catches the nutrients before it goes into the blood. That net is your liver.
So you've got the structure called the portal vein that feeds into the liver nutrients and kind of the food stuffs and particulates that are essentially being metabolized and digested. And the liver metabolizes all of this stuff, so to speak, and it processes it for your body to use. Drugs, for example, are metabolized by the liver.
And then, if you need sugar, all of a sudden then your liver metabolizes glycogen, breaks it down to create glucose so your body can use it when you need energy. If you eat too much sugar, the liver then turns it into glycogen so you can store it for later on. So it does a lot of this metabolism, kind of the heart of metabolism is the liver. It's also my favorite organ. Every time I read about it or look into it, I learn something new about it, all the time. It's important for fatty acid synthesis, fatty acid metabolism. It does a lot of really cool metabolic things.
Host Amber Smith: So where do the enzymes come in?
Akshay Patel: Enzymes, I guess broadly speaking, enzymes kind of facilitate reactions from happening, right?
So I'm looking at my headphones on my desk right now. Maybe if I stood here with my hand out 10 billion years from now those headphones would be in my hand, or I could just move my hand and the headphones would be in my hand. I had to put some energy into the system for the headphones to actually get into my hand. That's kind of what enzymes do. They use energy to facilitate a reaction from happening, converting some metabolite or some chemical into something else.
The liver is full of such enzymes. For those who are really into the nitty gritty, there's things called cytochrome oxidases that are important in metabolizing drugs.
You know, when we look at like, the pharmacogenetics, people with mutations in these enzymes are less likely to be able to metabolize certain drugs because of their mutations in the enzymes in the liver. So the liver is chock full of these machines that convert the molecules from one state into another state.
Host Amber Smith: And you mentioned the enzyme that you're studying -- rab4a. Do you know yet why it increases in patients with lupus?
Akshay Patel: Right. So rab4a, we have kind of focused on studying that in T-cells. So lupus is a primarily a T-cell driven disease. And probably 10, 15 years ago, our lab, -- I mean, I was in like 6th grade or something at this time, so I wasn't necessarily involved in this -- but other members of the lab previously found that this rab4a is increased in the T-cells of lupus patients. It's downstream of the signaling kind of cascade known as the mTOR cascade. So, mTOR is short for the mechanistic target of a rapamycin, kind of the central hub that senses amino acids and nutrients and metabolites inside of a cell.
And typically it's increased in states of inflammation, increased in states of autoimmunity, really because downstream what it does is it causes cell growth, cell expansion. And we don't want these autoimmune cells to grow and expand. We want them to stop expanding. So you can use something called rapamycin to inhibit mTOR, which then is able to essentially dampen the immune response, and it can control a lupus flare.
But rab4 is one of those things that was downstream of mTOR. The lab has been studying that quite some time now, and it's really, for the purposes of my experiments, it's important for two things. One, it's important for regulating mitophagy. Mitophagy is this process where mitochondria that are dysfunctional turnover. Because you don't want dysfunctional mitochondria that can produce oxidative stress, which, we're finding is a trigger of lupus pathogenesis. So what you want is the mitochondria to turn over. You don't want the bad mitochondria staying in there. What rab4 does is it decreases mitophagy. So when you have more rab4, you have less mitophagy. When you have less mitophagy, you have more dysfunctional mitochondria, which then leads to more oxidative stress. So it's kind of one arm of the whole rab4 story.
The other arm of the rab4 story is that it's an enzyme that's responsible for this thing called trafficking, where things are moved from one area of the cell to another area of the cell. And one such protein that is responsible for shuttling around the cell is this thing called CD4, which is on the surface of T-cells. It actually has the ability to bring CD4 from the surface to the T-cell and move it inside and target it for degradation into the lysosome, which inhibits its ability to actually work as an effective T-cell.
So this kind of has these two battling roles, one where it's responsible for promoting oxidative stress. Another one where it's responsible for kind of messing with the immune response.
Host Amber Smith: So let me ask you this. This rab4a enzyme, if you were able to remove that, would that reduce lupus from developing?
Akshay Patel: That's a great question. That is kind of what we're seeing in mice. So we have this mouse model of lupus called Sle123. It's got three major mutations. Sle1 is a mutation on chromosome one. Sle2 is a mutation on chromosome four. Sle3 is a mutation on chromosome seven. When all three of these things come together, you end up with mice that have kind of a critical outcome that is almost exactly like human lupus.
They have auto antibody production. They have renal dysfunction, renal involvement. And we created these mice to have two major genetic changes -- one where rab4a was constitutively activated, which kind of mimics human lupus, where human patients have overactive rab4a, and they have a lot of it.
Then we have this other mouse where we deleted rab4a in T-cells. So rab4a is up in T-cells, causes disease. So we hypothesized rab4a, deleted in T-cells, is going to rescue. It's not going to cause a disease. And for the major things that we look at, the major clinical outcomes that seemed to hold true. They have less autoantibodies, they have less protein in the urine. We call that proteinuria. It's a readout of renal involvement. And when we look at the kidney histology itself, we're seeing that the kidneys don't have as much damage. So I came into this thinking, "Hey, look, the livers are probably protected too."
And kind of that's where things got really wonky because we saw the exact opposite.
Over and over again, we saw that when we deleted rab4a from T-cells, they not only have more liver inflammation, this liver inflammation is marked by T and B cells, which are kind of the hallmark immune cells that are kind of dysfunctional in lupus, and we're seeing an increase in fatty acids in these livers, which is also a marker of liver inflammation. So that was really interesting. Very unexpected. And it was very difficult for us to try to explain it, but we have some ideas.
Host Amber Smith: That's interesting. And going forward, using the grant that you received, are you going to be doing more research that involves the rab4a enzyme?
Akshay Patel: Yeah, absolutely. So, my grant funding was for two years. It's for my final year of my PhD, which is now and my third year of medical school. So I'm kind of winding down on my experiments. Since I got the grant, we've made quite a bit of progress to kind of explain what's happening.
One is the metabolic side of things. We're seeing fatty liver. And we're seeing that this is downstream of mTOR. We're seeing a very specific protein being increased called SREbp1. It's a sterol regulatory element-binding protein 1, I think is what it stands for. And really it's responsible for fatty acid synthesis. So remember, I said there was more liver inflammation. There was also more fatty acids in these livers. And we're seeing a very specific protein that causes fatty acid accumulation that's building up in the livers of these mice where we deleted rab4a from their T-cells.
And what's interesting is that their fat kind of goes away. This protein that causes fatty acid buildup, it goes away when we treat these mice with rapamycin, which is kind of the hallmark treatment of lupus in humans, is rapamycin. And so it's very interesting to see that what we're seeing in humans, we're able to see it again in mice. And the treatments that we use in humans and in our patients in the clinic also holds true in these mice where they have this fatty acid buildup, and it's going away as a result of rapamycin.
Then there's also the immune side. Because remember, rab4a is deleted in T-cells, and what we're seeing is that when we delete rab4a in T-cells, there's a very particular cell type that not only is it contracted, so there's less of it. Also what we have is dysfunctional. And that's called the regulatory T-cell, which is kind of the anti-inflammatory immune cell of the body. So it's very weird, again, that we're seeing more of this liver inflammation. We're seeing more of this T-cell and B-cell infiltration into the livers of these mice. And we're seeing a defect in the anti-inflammatory arm of their immune system.
Because really, the immune response is, it's a delicate balance. It has to start off pro-inflammatory to fight off the invader. You can't keep having an immune response over and over again, because that's going to tire out the cells. You have to tell them to take it easy and take a chill pill. And regulatory T-cells do that. But we're finding that if we delete rab4a in T-cells, their regulatory T-cells, they don't have as many, and they don't work as well. The ones that are there don't work as well. So we've done functional studies on that, and I think the missing link between these two arms is soluble mediators of inflammation called cytokines.
Cytokines are like messenger packets where immune cells kind of interact with each other by sending each other notes, like in class. They're sending each other notes. These note packets are called cytokines. They are these proteins that flow in the blood or in the serum, and they bind to receptors on different types of cells to kind of mediate damage. And so that's kind of one area of exploration that I'm currently interested in. And I think we're making some progress there.
Host Amber Smith: It sounds like it. And it sounds like there's a lot to keep you busy working on, too. Thank you so much, mr. Patel, for taking time to explain this to us.
Akshay Patel: I'm happy to talk about my research. Thanks for having me.
Host Amber Smith: My guest has been Akshay Patel. He's an MD/PhD student working in the lab of Upstate's Dr. Andras Perl. "The Informed Patient" is a podcast covering health, science and medicine, brought to you by Upstate Medical University in Syracuse, New York, and produced by Jim Howe. Find our archive of previous episodes at Upstate.edu/informed. This is your host, Amber Smith, thanking you for listening.